[llvm-commits] [llvm] r154431 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/X86/fdiv.ll

[Duncan Sands]

Author: baldrick
Date: Tue Apr 10 15:35:27 2012
New Revision: 154431

URL: http://llvm.org/viewvc/llvm-project?rev=154431&view=rev
Log:
Add a comment noting that the fdiv -> fmul conversion won't generate
multiplication by a denormal, and some tests checking that.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/test/CodeGen/X86/fdiv.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=154431&r1=154430&r2=154431&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue Apr 10 15:35:27 2012
@@ -5769,9 +5769,9 @@
     APFloat N1APF = N1CFP->getValueAPF();
     APFloat Recip(N1APF.getSemantics(), 1); // 1.0
     APFloat::opStatus st = Recip.divide(N1APF, APFloat::rmNearestTiesToEven);
-    // Only do the transform if the reciprocal is not too horrible (eg not NaN)
-    // and the reciprocal is a legal fp imm.
-    if ((st == APFloat::opOK || st == APFloat::opInexact) &&
+    // Only do the transform if the reciprocal is a legal fp immediate that
+    // isn't too nasty (eg NaN, denormal, ...).
+    if ((st == APFloat::opOK || st == APFloat::opInexact) && // Not too nasty
         (!LegalOperations ||
          // FIXME: custom lowering of ConstantFP might fail (see e.g. ARM
          // backend)... we should handle this gracefully after Legalize.

Modified: llvm/trunk/test/CodeGen/X86/fdiv.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/fdiv.ll?rev=154431&r1=154430&r2=154431&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/fdiv.ll (original)
+++ llvm/trunk/test/CodeGen/X86/fdiv.ll Tue Apr 10 15:35:27 2012
@@ -23,3 +23,19 @@
   %div = fdiv double %x, 0.0
   ret double %div
 }
+
+define double @denormal1(double %x) {
+; Don't generate multiplication by a denormal.
+; CHECK: @denormal1
+; CHECK: divsd
+  %div = fdiv double %x, 0x7FD0000000000001
+  ret double %div
+}
+
+define double @denormal2(double %x) {
+; Don't generate multiplication by a denormal.
+; CHECK: @denormal
+; CHECK: divsd
+  %div = fdiv double %x, 0x7FEFFFFFFFFFFFFF
+  ret double %div
+}